In situ saphenous vein bypass is a procedure in which the saphenous vein in a human leg, which normally returns blood from the ankle upwardly through the leg, takes over the function of the femoral artery in the leg after the femoral artery has become too occluded, or otherwise impaired, to transport the flow of blood required of it.
When the saphenous vein is to be used to take over the function of the femoral artery, it becomes necessary to cut open the series of one-way valves which exist in the saphenous vein. These one-way valves in normal functioning prevent reverse flow of blood to the saphenous vein. In other words, the one-way valves permit flow of blood in the saphenous vein from the ankle to the thigh but do not permit the flow of blood in the opposite direction, which is otherwise required when the saphenous vein is to function in place of the femoral artery.
Accordingly, various valve strippers have been developed for cutting venous valves in situ in a patient's saphenous vein. Some of these valve strippers use a valve cutter which is passed through the vein in a direction opposite to the normal direction of venous blood flow through the vein to sever the valves. Examples of such valve cutters include the LaMaitre valvulotome, made by Vascutech of Massachusetts; the Hall vein stripper, made by Cabot Ltd. of High Wycombe, England; and the Leather valve cutter, made by American V. Mueller of Chicago, Ill.
Unfortunately, the valve strippers noted above operate blindly. Specifically, they are passed through the vein by a surgeon who does not directly observe the stripper or vein as the cutters operate. It will accordingly be appreciated that while such devices can perform quite satisfactorily in the hands of an experienced cardiovascular surgeon operating on a vein which does not have complications, blind incision of the valves has serious risks. For example, if the cutter's path veers off course into the side wall of the vein (this can happen without the ability to observe the vein directly), the blades can cut the delicate endothelial lining of the vein with serious adverse consequences. Also, side branches, i.e., veins entering the main vein from the side, may be caught by the valve cutter and torn open. This also causes serious injury.
To overcome the disadvantages of the so-called blind valve strippers noted above, an apparatus and method have been disclosed in U.S. Pat. No. 5,026,383 to Nobles that provides a fiber optic scope which is mounted in a valve cutter to view the valve cutter and adjacent tissue as the valve cutter travels through the vein. As envisioned by the Nobles device, a pulling catheter is inserted into the saphenous vein near the ankle and is passed in the normal direction of venous blood flow through the saphenous vein until its tip emerges through an exit opening created in the vein. A cutting catheter that has a cutting head comprising two spaced apart blades is then attached to the pulling catheter. Then, the pulling catheter can be pulled reversibly through the vein to cause the cutting blades to cut through the valves. The surgeon can make observations of the vein during the passage of the cutting catheter through the vein by means of the fiber optic scope.
In accordance with the Nobles device, the cutting catheter can be easily and quickly engaged with the pulling catheter. Also, the cutting head disclosed in the above-referenced Nobles patent is shaped to generally conform to the contours of the vein wall, thus reducing the risk that the cutting blade of the Nobles device will inadvertently cut the wall of the vein.
The Nobles device is generally satisfactory for the purposes for which it is intended. It happens, however, that the pulling catheter of devices such as the Nobles device can occasionally be difficult to pull through a saphenous vein. Thus, the present invention recognizes that it is desirable to provide a valvulotome that can be pushed through a saphenous vein.
Furthermore, the lumen of a saphenous vein ordinarily tapers gradually inwardly, from the thigh to the ankle. Thus, it will be appreciated that a cutting head which is large enough to efficaciously cut valves in a saphenous vein in the thigh of a patient may be too large to be pushed through the relatively narrower portion of the saphenous vein near the ankle of a patient. In other words, the present invention recognizes that a cutting blade, having only a single size, cannot optimally be used to cut valves in the saphenous vein, both in the thigh of a patient and near the ankle of a patient.
Accordingly, it is an object of the present invention to provide an optical valvulotome which has a cutting head that is detachable from the remainder of the valvulotome.
Another object of the present invention is to provide an optical valvulotome which can provide a video display of the interior of the vein during an in situ saphenous vein bypass procedure.
An additional object of the present invention is to provide an optical valvulotome which is easy to use and cost effective to manufacture.